Abstract: The welding of micro-components requires the welding power source to have high control accuracy and excellent dynamic characteristics. The precision and stability of the resistance spot welding power must be promoted so that the welding quality can be improved. Therefore, the high frequency inverter resistance spot welding power supply based on DSP is designed. dsPIC30F6010A is the control core of the power. The limited bipolar control scheme is used in the main inverter circuit. PWM is adopted to adjust welding current features. Limited Increment Form PI is also used in the control system to improve the precision of PWM control. The PI parameters are changed continuously to produce three-segment current, so the welding current can be precisely adjusted. The components of the power control system and the working principle of the limited bipolar control are introduced. The digital PWM generation and digital PI adjustment are described in detail and verified by tests. In the tests, the waveform of the driving voltage of inverter circuit is detected and it is proved that the welding voltage and current is stable under different parameters. It is also confirmed that the control system is stable and reliable, and has high control accuracy and response speed, thus satisfying the welding process requirements, which results in good performance of welding products.

Key words: Limited increment form proportion integration adjustment, Pulse width modulation control, High frequency, Inverter spot welding